PIX4Dsurvey allows for the project registration of imported data (point cloud or photogrammetry project in the form of point clouds and calibrated images) to an existing PIX4Dsurvey project. Any input data can be taken as a reference. This processing is optional but needs to be performed as the first step before proceeding with other processing (filters, grid of points, ...).

Automatic registration

The automatic registration is based on common features between the point cloud that need to be registered. No markers are needed to perform the registration.

Tool description

• [1] Reference Project: Choose a reference project from the drop-down list of available point clouds. The project registration will be based on this reference project.
• [2] Project to register: Choose a project to register from the drop-down list of available point clouds. The project chosen as a reference will not be available from this list.
  

  

  Dialog window for the Automatic project registration.

How to automatically register a project 

1. When using PIX4Dsurvey 1.47 and previous versions, click Register in the Content panel on the left of the PIX4Dsurvey window.
2. When using PIX4Dsurvey 1.48 and more recent versions, open the content sidebar and then, in the input data section , click on the Register... 
3. Select Automatic.
4. Select the Reference project from the drop-down menu. This project will serve as a reference.
5. Select the Project to register from the drop-down menu. This project will be registered.
6. Click Register.

Manual registration

(PIX4Dsurvey 1.48 and later versions) The Manual registration uses markers to register a point cloud with respect to a reference point cloud.

Tool description

• [1] Reference project: Choose a reference project from the drop-down list of available point clouds. This project will be used as reference, it won't be moved.
• [2] Project to register: Choose a project to register from the drop-down list of available point clouds. This project will be moved. The project chosen as a reference will not be available from this list.
• [3] Select reference marker: These markers serve as a reference for manual registration and should have been created on well-identifiable features.
• [4] Select matching marker:  These markers will be used pairwise to define the rotation and translation of the registration. Markers in the left column should have been created on the reference project. Markers from the right column should have been created on the project to register. Each pair of markers (left + right column) should indicate the same real-world point.
• [5] Add reference point: To be used if the user wants to use more than 3 markers to manually register a project. At least 3 markers are necessary to define an unambiguous transformation.
  

  

  Dialog window for the Manual project registration.

How to manually register a project

1. Create at least three markers on well-identifiable features in the point cloud of the reference project (Vectorization tools in PIX4Dsurvey). These points should also be visible on the project to register.
   1. Navigate in the 3D view.
   2. Press M to enable the marking vectorization.
   3. Click on the well-identifiable feature on your reference projects' point cloud to create the marker.
   4. (optional) Rename the marker to make it recognizable.
   5. Repeat for at least two other points.
2. Create markers for the same features as in step 1 (Vectorization tools in PIX4Dsurvey).
   1. Navigate in the 3D view to find the same features identified in the previous step.
   2. Press M to enable the marking vectorization.
   3. Click on the well-identifiable feature on the point cloud of the project to register to create the marker.
   4. (optional) Rename the name to make it recognizable.
   5. Repeat for all other markers identified in the reference project.
   Tip: Use the visibility buttons and in the input data section in the content panel to view/hide a specific project. This will help when creating markings on the reference project or on the project to register. Learn more about visibility in this article: Project management > Content Management.
3. Open the content sidebar and then, in the input data section , click on the Register... 
4. Select Manual.
5. Select the project that will serve as a reference from the Reference project drop-down menu. This project must be the one used to create the markers in step 1.
6. Select the project that will need to be registered from the Project to register drop-down menu. This project must be the one used to create the markers in step 2.
7. Select the Reference markers; these should be the markers created in step 1.
8. Select the Matching markers; these should be the markers created in step 2.
   
    

   Important: The Reference markers and Matching markers referring to the same feature must be entered on the same row.
9. (optional) Click Add reference point to add more reference point markers in case you created more than three markers in steps 1 and 2.
10. Click Register.